Merge pull request #15 from dreipunktnull/vh_media

[FEATURE] Added image width, height and mimetype view helpers
[FEATURE] Iterator / Values ViewHelper

Extracts raw values from Traversable/Arrays, removing any keys and turning the output into a raw Array.
[FEATURE] Iterator / Merge ViewHelper

Merges two Traversable/Array instances into one raw Array, returning that array or inserting it as a template variable while rendering the child content if using the "as" argument.
[DOC] Use Markdown in Doc Comments (1)

Work in progress to be committed in smaller chunks. All Doc Comments are being turned into Markdown syntax for automatic rendering in online documentation.